Respiratory mask



FIG. 1 is a perspective view, showing the new design for a respiratory mask;

FIG. 2 is a left side view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof.

The broken line showing forms no part of the claimed design. 

CLAIM The ornamental design for a respiratory mask, as shown and described. 